This invention relates in general to vehicle wheels and in particular to two piece wheels having a wheel rim mechanically attached to a wheel disc with a press fit.
It is known in the art to fabricate a vehicle wheel by attaching a wheel rim to a separately formed wheel disc. Typically, the wheel rim is rolled from steel strip stock and the disc is stamped from steel sheet stock. The rim is welded to the disc to form the wheel. Such a wheel is shown in U.S. Pat. No. 5,257,455 to Iwatsuki. Alternately, the wheel rim can be rolled from steel and the wheel disc cast or forged from a light weight metal, such as aluminum, titanium or magnesium, or an alloy of a light weight metal. Because the metals forming the rim and disc are different, a ferrous weld anchor is usually attached to the wheel disc. The wheel rim is welded to the weld anchor to assure that a good weld is formed between the rim and disc. Such a wheel is described in U.S. Pat. No. 3,506,311 to Nobach and is commonly referred to as a bimetal wheel. A bimetal wheel combines the economy, flexibility and strength of a steel wheel rim with the pleasing ornamental appearance of three dimensional contours formed in a cast or forged wheel disc.
To enhance the appearance of a two piece bimetal wheel, it is known to attach a fall face wheel disc, which includes the outboard tire retaining flange, to a partial wheel rim to form a full face bimetal wheel. When a tire is mounted upon a full face wheel, the joint between the wheel disc and wheel rim is completely hidden and only the wheel disc is visible. A decorative finish is often applied to the face of the wheel disc to further enhance the appearance of the wheel. Examples of typical decorative finishes include metal plating, such as chromium plating, clear coatings and paint.
Referring now to the drawings, there is shown in FIG. 1 a fragmentary sectional view of a typical prior art bimetal full face wheel 10. The wheel 10 is described in the Nobach patent listed above and includes a full face wheel disc 11 formed from a light weight metal or light weight metal alloy by a conventional process, such as gravity, low pressure or die casting. The full face wheel disc 11 includes a central wheel hub 12 which is supported by a plurality of wheel spokes 13 (one shown) within an annular sidewall 14. An outboard tire bead retaining flange 15 extends in a radial outward direction from the sidewall 14.
A ring-shaped weld anchor 16 formed from a ferrous material, such as steel, is partially embedded in the wheel disc sidewall 14. A portion of the weld anchor 16 is exposed to form a welding surface 17. The sidewall 14 further includes a cylindrically-shaped shoulder 18 which extends axially from the inboard side of the flange 15. The shoulder 18 extends radially over a portion of the weld anchor 16 to secure the weld anchor 16 to the wheel disc 11.
A conventional partial wheel rim 20 is attached to the inboard side of the wheel disc 11. The wheel rim 20, which is formed from steel strip stock with conventional rim roll forming machinery, includes an inboard end 21 terminating in a conventional inboard tire bead retaining flange 22. An inboard tire bead seat 23 and inboard safety bead 23A are also formed on the inboard end 21 of the wheel rim 20. A leg portion 24 extends in an outward axial direction from the inboard safety bead 23A. A deepwell 25 is formed in the wheel rim 20 adjacent to the leg portion 24. The wheel rim 20 also includes a cylindrically-shaped outboard end 26 which is adjacent to the deepwell 25. The outboard wheel rim end 26 includes an outboard tire bead seat 27 and outboard safety bead 27A. The outboard rim end 26 extends over the wheel disc shoulder 18 and into contact with the welding surface 17 of the weld anchor 15. The outboard rim end 26 and the wheel disc collar 18 are typically sized to form a clearance fit therebetween, allowing the wheel rim 20 to be rotated relative to the wheel disc 11.
An alternate structure for the weld anchor is disclosed in U.S. Pat. No. 5,421,642 to Archibald where the weld anchor includes an annular collar which is received by the outboard end of a partial wheel rim. The weld anchor collar positions the wheel rim upon the wheel disc.
A continuous circumferential air-tight weld 28 is formed between the wheel rim 20 and the weld anchor 16. Typically, a conventional friction or inertial welding process is used to form the weld 28. During the welding process, the wheel disc 11 is held stationary while the wheel rim 20 is rotated with the outboard wheel rim end 26 pressed against the weld anchor 16. The heat generated by friction partially melts the wheel rim end 26 and the adjacent portion of the weld anchor 16 to form the weld 28.
While the wheel disc is typically welded to the wheel rim, it is also known to heat shrink the wheel rim onto the wheel disc, as shown in U.S. Pat. No. 4,363,347 to Baumgartner and European Patent Application No. 0 096 399 to Stahlschmidt & Malwurm GmbH & Co. KG. The U.S. Patent discloses wheel structures having either cylindrical or conical shrinkage surfaces. The U.S. Patent also discloses optional cutting or rolling of threads on the cylindrical shrinkage surfaces to allow the disc to be threadedly attached to the wheel rim. The European Patent Application discloses conical shrinkage surfaces. The European Patent Application further discloses optional forming of cleats and corresponding grooves, which receive the cleats, on the shrinkage surfaces.